Several years ago, I participated in the GLOW 5K in College Station, Texas. It was an experience that would inspire me for years to come and encourage me to run more in the future.
First off, it's a night time race - no early morning to risk oversleeping for. Glow sticks and bright colors abound to raise money for two charities (supported by the student organizations that put it on).
When I participated (at this point I walked most of it, as I was not an avid runner), it was one of the largest races at Texas A&M, and I think it has stayed that big since. I loved that it was walker friendly, of course, but several competitive runners from the Texas A&M teams also raced, so there were all different backgrounds at the race. There was a little congestion at the starting line, but other than that, the crowd thins out and you're able to get around. Given that it's in February, it was nice and cool outside, and the course was relatively flat with maybe 1-2 hills. Swag is okay - the shirt designs are always cool and bright, and there is free Jamba Juice and Chick Fil A. They are not tech shirts, but the price of admission is only $15 (a steal) and it includes your glow stick and bib number. There are also prizes if you win Male or Female category.
Overall, you really can't beat the fun atmosphere of this race and I have recommended it to so many people. The student organizations who put it on are full of energy and put a lot of work into making it truly a FUN run. It's a blast and it supports great causes for people in need!